Tube squaring machines are required to precision cut a square surface at the end of a piece of pipe or a tube, such that a precision weld can be made for attachment of the pipe or tube end to a fitting or to an adjacent length of pipe or tube. Similarly, squaring machines are used to cut a square surface at the end of a fitting for the attachment of a fitting to a length of pipe or tube. In many cases, a tube or fitting must have a square end and the cut must be to an exact length.
Existing squaring machines grip the end of the tube in a collet to hold the axis of the tube aligned with the axis of a rotating cutter which will remove a portion of the metal at the end of the tube, such that the end thereof will be square. Existing squaring machines, however, do not have a means for precision indexing the feed of the tool, and the feed of such machines can not be adjusted to remove a predetermined amount of metal. An operator will frequently perform a series of machining operations, each time shearing off a small portion of the metal of the tube, removing the tube from the machine to measure its length, and then machine off more metal until the desire length of the tube has been reached. If care is not exercised, too much metal may be removed and the piece rendered useless.
In existing squaring machines, the feed is controlled by a handle which rotates a cam to move the tool against a work piece. Such cam operated feeds to not provide a linear relationship between the advancement of the feed and the angle of the handle, and as a result, the operator can not determine the distance that the feed has advanced by observing the angle through which the handle has been rotated.
Furthermore, to cut a square end to a piece of pipe or tubing, existing machines have a collet retainer at the end of the machine for receiving a collet to clamp the end of the tube in the desired orientation. Such retainers have a tapered bore into which a complementary shaped frustoconical collet is fitted, and a nut is threaded over one end of the retainer to force the collet within the tapered bore to compress it around a pipe or tube. To retain the end of a work piece in such a squaring machine, one must first slide the retaining nut over the work piece, fit the end of the work piece into a collet, fit the collet with the work piece therein into the tapered bore of the machine, and finally, tighten the nut against the collet.
Existing squaring machines also have a collet retainer of a given size, such that the maximum inner diameter of the pipe or tube which may be fitted into the machine is limited by the maximum diameter of the collet which the retainer on the machine can receive. On the other hand, the minimum diameter of a piece of tubing which can be squared by such machines is limited to the minimum diameter of a piece of tubing which can be grasped by a collet having a given outer diameter. As a result, if one wishes to square the ends of a wide range of sizes of tubes, one must use a plurality sizes of tube squaring machines.
Existing collets are generally made of a unitary piece of metal having elongate slots in the length thereof, such collets permit little expansion of the inner diameter from the compressed position in which the collet is locked against the outer surface of a work piece, and the relief position, in which the work piece can be removed from the collet.
It would be desirable to provide a squaring machine for which the feed can be accurately measured and controlled. Also, it would be desired to provide a squaring machine which can be used to square the ends of tubing, or fittings, having a wide range of sizes.
It would also be desirable to provide a collet for use in such a machine in which the expanded, relief position thereof is substantially larger than the compressed locked position, and further provide a collet which can be more easily fitted around a work piece than existing collets.